Many petroleum refining and chemical production processes include one or more separation processes for isolating desirable products. Membrane separations are a potentially desirable method of separation due to the low energy requirements for performing a separation. However, use of membrane separations is limited to situations where a suitable membrane is available for performing a commercial scale separation.
Separation of para-xylene from other C8 aromatics is an example of a separation that is difficult to perform via a boiling point separation. Current commercial methods involve selective crystallization or simulated moving bed chromatography to separate para-xylene from ortho- and meta-xylene. These methods are energy and/or equipment intensive.
U.S. Pat. No. 4,510,047 describes regenerated cellulose membranes for use in reverse osmosis separation of hydrocarbonaceous compounds, such aromatic extraction solvents. The regenerated cellulose membranes are susceptible to pore swelling in the presence of such solvents.
U.S. Pat. No. 4,571,444 describes methods for separating alkylaromatic compounds from aromatic solvents using asymmetric polyimide fiber membranes. The membrane is described as being suitable for at least partially separating benzene, toluene, and/or ethyl benzene from single ring aromatic compounds that are alkylated with a C8 to C20 alkyl group.